King James Version
Wherefore? Because they sought it not by faith, but as it were by the works of the law. For they stumbled at that stumblingstone;English Standard Version
Why? Because they did not pursue it by faith, but as if it were based on works. They have stumbled over the stumbling stone,New International Version
Why not? Because they pursued it not by faith but as if it were by works. They stumbled over the "stumbling stone."